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        <section id="main"><article id="post-JavaScript进阶知识点-JS函数深入" class="article article-type-post" itemscope itemprop="blogPost">
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    <a href="/2019/09/14/JavaScript进阶知识点-JS函数深入/" class="article-date">
  <time datetime="2019-09-14T02:38:33.000Z" itemprop="datePublished">2019-09-14</time>
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    <a class="article-category-link" href="/categories/JavaScript/">JavaScript</a>
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      JavaScript进阶知识点--JS函数深入
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<h1 id="对象"><a href="#对象" class="headerlink" title="对象"></a>对象</h1><h2 id="创建对象（P145）"><a href="#创建对象（P145）" class="headerlink" title="创建对象（P145）"></a>创建对象（P145）</h2><ol>
<li><p>字面量方法</p>
</li>
<li><p>构造函数</p>
</li>
<li><p><code>Object.create()</code></p>
</li>
</ol>
<h2 id="删除对象属性"><a href="#删除对象属性" class="headerlink" title="删除对象属性"></a>删除对象属性</h2><blockquote>
<p>delete obj.attributeName</p>
</blockquote>
<h2 id="检测属性是否在对象中"><a href="#检测属性是否在对象中" class="headerlink" title="检测属性是否在对象中"></a>检测属性是否在对象中</h2><blockquote>
<p>attributeName in obj</p>
</blockquote>
<p>例：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">var person = &#123;</span><br><span class="line">    name: &quot;Tom&quot;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">console.log(name in person);// true</span><br></pre></td></tr></table></figure>

<h2 id="对象枚举"><a href="#对象枚举" class="headerlink" title="对象枚举"></a>对象枚举</h2><h3 id="for-in-循环（P57）"><a href="#for-in-循环（P57）" class="headerlink" title="for in 循环（P57）"></a>for in 循环（P57）</h3><h1 id="函数"><a href="#函数" class="headerlink" title="函数"></a>函数</h1><h2 id="字面量"><a href="#字面量" class="headerlink" title="字面量"></a>字面量</h2><ul>
<li><p>function 声明</p>
</li>
<li><p>var 赋值表达式</p>
</li>
</ul>
<h3 id="区别"><a href="#区别" class="headerlink" title="区别"></a>区别</h3><p>var 赋值表达式不能写在调用之后</p>
<p>var 赋值表达式要先定义，后调用</p>
<h2 id="构造函数（不建议）"><a href="#构造函数（不建议）" class="headerlink" title="构造函数（不建议）"></a>构造函数（不建议）</h2><p>例：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">var fun = new Function(&quot;num1&quot;, &quot;num2&quot;, &quot;return num1 + num2&quot;)</span><br></pre></td></tr></table></figure>

<h2 id="直接函数调用"><a href="#直接函数调用" class="headerlink" title="直接函数调用"></a>直接函数调用</h2><ul>
<li><p>普通函数调用</p>
</li>
<li><p>匿名函数调用（不能让function打头）（也叫自执行函数）</p>
</li>
</ul>
<h2 id="间接函数调用"><a href="#间接函数调用" class="headerlink" title="间接函数调用"></a>间接函数调用</h2><ul>
<li><p>fun.call()</p>
</li>
<li><p>fun.apply();</p>
</li>
</ul>
<h3 id="参数"><a href="#参数" class="headerlink" title="参数"></a>参数</h3><ol>
<li><p>第一个参数：改变this的指向</p>
</li>
<li><p>第二个参数：改变参数的值</p>
<ul>
<li><p>call：传进的参数以逗号分隔</p>
</li>
<li><p>apply：传进的参数以数组形式体现</p>
</li>
</ul>
</li>
</ol>
<p>例：</p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">// call 方法调用</span><br><span class="line">fun.call(window, 1, 2);</span><br><span class="line"></span><br><span class="line">// apply 方法调用</span><br><span class="line">fun,apply(window, [1, 2]);</span><br></pre></td></tr></table></figure>

<h1 id="注意"><a href="#注意" class="headerlink" title="注意"></a>注意</h1><ul>
<li><p>如果用 alert 或 document.write 输出不是字符串的值，则该值则调用 <code>toString()</code> 方法</p>
</li>
<li><p>document.write 期望接收和输出字符串，当接收的参数不为字符串时，会调用参数的<code>toString</code>方法，将其转化成字符串输出</p>
</li>
<li><p>数组调用<code>toString()</code>后，会将其中的元素用逗号拼接起来变成字符串</p>
</li>
<li><p>一般的对象调用toString()后返回<code>[object Object]</code></p>
</li>
</ul>

      
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